Effect of Cationic Substitution on Raman Spectra of SrBi2Ta2O9Ceramics and Thin Films

2003 ◽  
Vol 784 ◽  
Author(s):  
W. Perez ◽  
R. R. Das ◽  
P. S. Dobal ◽  
Y. I. Yuzyuk ◽  
P. Bhattacharya ◽  
...  
Keyword(s):  
Thin Films ◽  
Transition Temperature ◽  
Lattice Mismatch ◽  
Ferroelectric Properties ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Cationic Substitution ◽  
Factor Substitution ◽  
Raman Modes

ABSTRACTIn the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1and 58 cm-1showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2planes inside the stable perovskite unit of SrTa2O7which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.

Structural and Ferroelectric Properties of Bi4-xNixTi3O12 Thin Films by Sol-Gel Process

2006 ◽  
Vol 966 ◽  
Author(s):  
Ricardo Melgarejo ◽  
Maharaj S Tomar ◽  
Rahul Singhal ◽  
Ram S Katiyar
Keyword(s):  
Thin Films ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
Coating Materials ◽  
Low Field ◽  
Sol Gel Process ◽  
Raman Modes ◽  
Ferroelectric Memories

ABSTRACTNickel-substituted Bi4Ti3O12 (i.e., Bi4-xNixTi3O12) were synthesized by sol-gel process for different compositions. Thin films were deposited on Pt (i.e., Pt/TiO2/SiO2/Si) substrate by spin coating. Materials were characterized by x-ray diffraction and Raman spectroscopy. This study indicates that the material makes a solid solution for the compositions: x = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.30, where a Ni ion replaces the Bi site. The prominent effect of Ni substitution was observed in low-frequency Raman modes. Sol-gel derived thin films of Bi4-xNixTi3O12 on a Pt substrate and post annealed at 700°C were tested for ferroelectric response which showed high remnant polarization (Pr = 22 μC/cm2 for x = 0.15). The leakage current (less then 10−7 A/cm2) at low field was observed in the film with composition x = 0.15 .The polarization of the BNiT (x = 0.15) film decreased to 83% of the initial value after 1×109 switching cycles These results indicate the potential application of Ni substituted bismuth titanate films in non-volatile ferroelectric memories.

Effect of Bottom Electrodes on Structural and Electrical Properties of Laser Ablated SrBi2Ta2O9 Thin Films

2001 ◽  
Vol 688 ◽  
Author(s):  
Rasmi R. Das ◽  
W. Pérez ◽  
P. Bhattacharya ◽  
Ram. S. Katiyar
Keyword(s):  
Thin Films ◽  
Barrier Height ◽  
Ferroelectric Properties ◽  
High Resistivity ◽  
Emission Model ◽  
X Ray Diffraction ◽  
Oxide Electrodes ◽  
Maximum Value ◽  
Structural And Electrical Properties ◽  
Raman Modes

AbstractWe have grown SrBi2Ta2O9 (SBT) thin films on various bottom electrodes such as Pt/TiO2/SiO2/Si (Pt) and LaNiO3/Pt/TiO2/SiO2/Si (LNO) substrates. The substrate temperature and oxygen pressure for the SBT film was maintained at 500 °C and 200 mTorr. As-grown films were post-annealed at a temperature of 800 °C. X-ray diffraction studies revealed that as-grown films were amorphous and crystallized to single phase after annealing. The difficulty of obtaining lowest Raman modes of SBT on platinized silicon substrate was overcome by using conducting oxide electrodes. Films grown on platinized silicon showed maximum value of remanent polarization (2Pr ∼ 21.5 μC/cm2) with coercive field (Ec) of ∼ 67 kV/cm. The degradation of ferroelectric properties of the films was observed with the introduction of 50 nm conducting LaNiO3 electrode at the interface of Pt and SBT film, which was attributed to high resistivity of the oxide electrode layers. Leakage current density was studied with the consideration of the Schottky emission model. The barrier height of the films grown on Pt and LNO were estimated to be 1.27 eV and 1.12 eV, respectively. The reduction of barrier height was attributed to the lower work function of the LNO electrode.

Ferroelectric memory in La substituted Bi4Ti3O12 thin films

2003 ◽  
Vol 784 ◽  
Author(s):  
R. E. Melgarejo ◽  
M. S. Tomar
Keyword(s):  
Thin Films ◽  
Film Growth ◽  
Sol Gel ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Modes ◽  
La Substitution ◽  
Ferroelectric Memory ◽  
Recent Demonstration

ABSTRACTThe recent demonstration of large ferroelectric memory in rare earth substituted Bi4Ti3O12 attracted a lot of research interest in this material. Bi4-xLaxTi3O12 was synthesized by sol-gel route for different compositions: x = 0.00, 0.46, 0.56, 0.75, 0.95 and thin films were deposited by spin coating on Pt (Pt/TiO2/SiO2/Si) substrate. The post annealed films at 700°C were studied for their structural studies using x-ray diffraction and Raman spectroscopy. The prominent effect of La substitution is observed in low frequency Raman modes. X-ray diffraction and Raman studies show that the film growth was c-axis suppressed. Using improved contacts to Pt substrate, ferroelectric polarization Pr = 51 μC/cm2 has been achieved for 0.63 μm thick film of composition: x = 0.56 (BLT56) without appreciable fatigue.

scholarly journals Creating better superconductors by periodic nanopatterning

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
Milan Allan ◽  
Mark H Fischer ◽  
Oliver Ostojic ◽  
Arjo Andringa
Keyword(s):  
Thin Films ◽  
Transition Temperature ◽  
Numerical Methods ◽  
Model Calculation ◽  
Lattice Mismatch ◽  
Specific Pattern ◽  
Design Parameters ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Correct Design

The quest to create superconductors with higher transition temperatures is as old as superconductivity itself. One strategy, popular after the realization that (conventional) superconductivity is mediated by phonons, is to chemically combine different elements within the crystalline unit cell to maximize the electron-phonon coupling. This led to the discovery of NbTi and Nb_33Sn, to name just the most technologically relevant examples. Here, we propose a radically different approach to transform a ‘pristine’ material into a better (meta-) superconductor by making use of modern fabrication techniques: designing and engineering the electronic properties of thin films via periodic patterning on the nanoscale. We present a model calculation to explore the key effects of different supercells that could be fabricated using nanofabrication or deliberate lattice mismatch, and demonstrate that specific pattern will enhance the coupling and the transition temperature. We also discuss how numerical methods could predict the correct design parameters to improve superconductivity in materials including Al, NbTi, and MgB_22.

Low-frequency excess noise in YBCO thin films near the transition temperature

1993 ◽  
Author(s):  
Sisi Jiang ◽  
Peter Hallemeier ◽  
Charles Surya ◽  
Julia M. Phillips
Keyword(s):  
Thin Films ◽  
Transition Temperature ◽  
Low Frequency ◽  
Excess Noise ◽  
Ybco Thin Films

Structural and Electrical Properties of Colossal Magnetoresistive LSMO Thin Films Prepared by KrF Laser Ablation Method

2001 ◽  
Vol 666 ◽  
Author(s):  
Fumiaki Mitsugi ◽  
Tomoaki Ikegami ◽  
Kenji Ebihara ◽  
Jagdish Narayan ◽  
Alexander M. Grishin
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Electrical Properties ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Axis Orientation ◽  
X Ray ◽  
Colossal Magnetoresistive ◽  
Laser Ablation Method ◽  
Structural And Electrical Properties

ABSTRACTWe prepared colossal magnetoresistive La0.8Sr0.2MnO3 thin films on the MgO, SrTiO3 and LaAlO3 single crystal substrates using KrF excimer pulsed laser ablation technique. The structural and electrical properties of the La0.8Sr0.2MnO3 thin films which were strained by the lattice mismatch are reported. The in-plane lattice mismatch between the La0.8Sr0.2MnO3 and MgO, SrTiO3 and LaAlO3 substrates are -7.8 %, -0.5 % and +2.3 %, respectively. The X-ray diffraction spectra of the films exhibited c-axis orientation. In the case of the La0.8Sr0.2MnO3 / LaAlO3 thin films with thickness over 100 nm, the divided (00l) peaks were observed. The surface morphology and transport property of the strongly stressed La0.8Sr0.2MnO3 / LaAlO3 were different from those of La0.8Sr0.2MnO3 / MgO and La0.8Sr0.2MnO3 / SrTiO3thin films.

EFFECT OF GRAIN SIZE ON THE FERROELECTRIC PROPERTIES OF Bi3.25La0.75Ti3O12 Thin Films

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4469-4474 ◽  
Author(s):  
KYOUNG-TAE KIM ◽  
CHANG-IL KIM ◽  
DONG-HEE KANG ◽  
IL-WUN SHIM
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Remanent Polarization ◽  
Ferroelectric Properties ◽  
Fatigue Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Current Densities ◽  
Metalorganic Decomposition ◽  
Small Grains

The Bi 3.25 La 0.75 Ti 3 O 12 (BLT) thin films were prepared by metalorganic decomposition method. The effect of grain size on the ferroelectric properties during crystallization were investigated by x-ray diffraction and field emission scanning electron microscope. The grain size and the roughness of BLT films increase with increasing of drying temperature. The leakage current densities of the BLT thin film with large grains are higher than that with small grains. The remanent polarization of BLT increase with increasing grain size. As compared BLT with small grain size, the BLT film with larger grain size shows better fatigue properties. This may be explained that small grained films shows more degradation of switching charge than large grained films.

Structural and Vibrational Properties of Ferroelectric Pb1-xSrxTiO3 Thin Films and Powders

2002 ◽  
Vol 748 ◽  
Author(s):  
M. Jain ◽  
A. Savvinov ◽  
P. S. Dobal ◽  
S. B. Majumder ◽  
R. S. Katiyar ◽  
...  
Keyword(s):  
Thin Films ◽  
Soft Mode ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Vibrational Properties ◽  
X Ray Diffraction ◽  
Phase Transition Temperatures ◽  
Induced Changes ◽  
Pst System

ABSTRACTIn this work we present the structural, and vibrational properties of ferroelectric Pb1-xSrxTiO3 (PST). Thin films of PST were prepared by using sol-gel technique for various compositions with x values ranging from 0.0–1.0. Respective compositions were also prepared in ceramic and powder forms using sol-gel and solid-state reaction methods. X-ray diffraction was used for the structural characterization of these materials. Raman spectroscopy was utilized to study the phases and lattice vibrational modes, especially the soft mode in PST compositions. The temperature dependence of the soft mode frequency for different PST compositions revealed that the phase transition temperatures increased with increasing Pb contents in PST system. Ferroelectric properties of the films were correlated with the substitution-induced changes in the material.

The ferroelectric properties of Cd2Nb2O7: a Monte Carlo simulation study

2011 ◽  
Vol 44 (3) ◽  
pp. 585-594 ◽  
Author(s):  
T. Malcherek
Keyword(s):  
Phase Transition ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Transition Temperature ◽  
Soft Mode ◽  
Ferroelectric Properties ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Monte Carlo Simulation Study ◽  
First Order Phase Transition

The order–disorder contributions to the ferroelectric properties of Cd2Nb2O7(CNO) have been studied by Monte Carlo simulation of a 12-state modified Potts model on the pyrochlore lattice. Spin configurations obtained by these simulations are mapped to local Nb displacements. Secondary Cd displacements normal to the Nb displacement directions are considered as well. The model correctly reproduces diffuse scattering experimentally observed in CNO. A first-order phase transition is observed forkTp/J= 0.3891 (kis the Boltzmann constant,Tpis the model phase transition temperature andJis the interaction energy). To further adapt the model to the properties of CNO, coupling of local Nb displacements to theT2usoft mode is simulatedviathe addition of an appropriate field term in the model Hamiltonian. The critical temperatureTcof the soft mode is scaled tokTc/J= 0.3704. Similarities to experimental observations,i.e.the occurrence of stable domains with {100} boundaries, as well as spontaneous polarization along the cubic 〈100〉 and 〈110〉 directions, indicate thatTpcan be associated with the transition temperatureT1= 205 K in CNO. Frequency dispersion of the dielectric permittivity of CNO can be attributed to the low-frequency switching of correlated chains of Nb displacement that remain partially disordered in the temperature range between 195 and ∼100 K.

Formation and structure of tin-iron oxide thin film CO sensors

1994 ◽  
Vol 9 (5) ◽  
pp. 1250-1256 ◽  
Author(s):  
P. Bonzi ◽  
L.E. Depero ◽  
F. Parmigiani ◽  
C. Perego ◽  
G. Sberveglieri ◽  
...  
Keyword(s):  
Thin Films ◽  
Structural Model ◽  
Large Range ◽  
Oxide Thin Film ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
X Ray ◽  
Co Sensor ◽  
Auger Microscopy ◽  
Pauling Electronegativity

Rheotaxial growth and thermal oxidation (RGTO) for depositing thin films is a recognized technique in preparing gas sensitive semiconducting oxides. This paper presents a study performed by x-ray diffraction and scanning Auger microscopy of the mechanisms of growth and formation of the thin films of the new ternary compound Sn1−xFexOy with an iron content in the range O < x < 25 at. %. A structural model of this compound, which is found to be stable over a very large range of Sn/Fe ratios, can be derived by partially substituting Fe3+ ions in Sn4+ sites. This is an easy substitution in view of the similar values shown by the ionic radii (Fe3+ = 0.64 Å, Sn4+ = 0.71 Å) and the Pauling electronegativity (Fe3+ = 1.8, Sn4+ = 1.8) of these two ions. Experimental data, showing that this material is an excellent CO sensor, are reported.

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